The characteristics of swollen lymph nodes are as follows: First, swollen lymph nodes are divided into local lymph node enlargement and systemic lymph node enlargement, which have different meanings. Generally, swollen local lymph nodes represent local inflammation or non-specific lymph node inflammation, as well as diseases such as cancer metastasis. If the lymph nodes are enlarged in more than two areas, it is called generalized lymph node enlargement, which often represents systemic diseases, such as connective tissue disease, infectious mononucleosis, and acute and chronic lymphadenitis. Secondly, swollen lymph nodes are characterized by pain. Severe swollen lymph nodes are usually caused by inflammation, while non-painful swollen lymph nodes are relatively more serious and are likely to be metastatic cancer, etc. Third, swollen lymph nodes are related to the blood flow of their corresponding lymphatic vessels, such as inflammation in the parts related to the lymphatic fluid received when the lymph nodes in the neck are swollen, and swollen lymph nodes under the jaw may have periodontitis, stomatitis, etc.